Defibrillation by strong electric shock remains the only known effective way of terminating ventricular fibrillation (VF) and, thus, preventing sudden cardiac death. However, strong shocks are associated with adverse effects including cellular injury from electroporation, cardiac conduction disturbances, mechanical dysfunction, increased mortality, and pain and psychological trauma. More than 100,000 implantable cardioverter-defibrillators (ICDs) are implanted annually in the United States alone. Regrettably, inappropriately delivered shocks remain common and over 13% of patients with an ICD receive one or more inappropriate shocks. The adverse effects of high-voltage shocks could be avoided or diminished if VF could be terminated reliably by defibrillation shocks of significantly lower voltage and energy. Hence, a method and device for low-voltage termination of VF would have important clinical applications.
Atrial fibrillation (AF), on the other hand, is the most common cardiac arrhythmia and can be chronic. AF can severely affect quality of life, and it can lead to severe complications such as stroke. The adverse effects of ventricular defibrillation hold true for atrial defibrillation as well, with two additional points to consider: 1) AF is not, per se, life-threatening, so the case for a potentially damaging therapy such as high-voltage defibrillation is not as strong as in VF, and 2) a strong defibrillation shock could induce potentially life-threatening ventricular arrhythmias. Hence, a method and device for low-voltage termination of AF would have potential clinical applications.
Recent experimental studies have shown that applied electric fields delivering multiple far-field stimuli can terminate ventricular tachycardia (VT), atrial flutter (AFl), and AF with less total energy than a single strong shock. Some of these studies used constant stimulation rates close to the arrhythmia cycle length (CL), whereas others used constant stimulation rates much faster than that CL. Since the mechanisms by which multiple far-field stimuli terminate arrhythmias are not well understood, it remains unknown which stimulation protocol (with constant or variable stimulation rates) would present the optimal benefit. Furthermore, it is unclear whether VF can also be terminated by multiple low-voltage, far-field stimuli.
It would therefore be advantageous to provide a method and device for low-voltage defibrillation of a patient.